Frequency Domain Method for Real-Time Detection of Oscillations.

Because of the growing interest in real-time stability monitoring, there is a need for online methods that can detect off-nominal behavior in control systems. Therefore, we present a real-time frequency domain method for detecting oscillations in control systems. The method uses recursive Fourier transform for representing the measured time-domain signal in frequency domain. Oscillations are then detected by monitoring the norm of the Fourier coefficients over a time window of prespecified size across a range of frequencies that represent off-nominal behavior for the plant. The method is computationally efficient and requires little memory, and hence suitable for online application. The feasibility of using this method for a real-time detection of oscillation is demonstrated on the Georgia Tech Twinstar Unmanned Aerial System.